Doctors usually recommend that adults whose asthma is poorly controlled by low doses of inhaled corticosteroids either increase their inhaled corticosteroids or supplement them with long-acting beta agonists. Neither solution is ideal. Higher doses of corticosteroids dont improve symptoms for all patients and can have significant side effects. The safety of long-acting beta agonists has come under serious scrutiny recently.

A research team led by Dr. Stephen Peters of the Wake Forest University Baptist Medical Center set out to test whether anticholinergic therapy could provide an effective alternative. Anticholinergic drugs help relax the airways by blocking a part of the nervous system that signals airway muscles to contract. Researchers have been exploring anticholinergic therapies in asthma, but this is the first study to test the addition of an anticholinergic inhaler to low-dose inhaled corticosteroids.

The researchers enrolled 210 adults whose asthma wasn't well-controlled with low doses of inhaled corticosteroids. They compared 3 treatments: doubling the dose of corticosteroids, supplementing the low-dose corticosteroids with a long-acting beta agonist (salmeterol) and supplementing low-dose corticosteroids with a long-acting anticholinergic drug (tiotropium bromide). The participants received each treatment for a 14-week period, followed by a 2-week "washout" period. The study was conducted at multiple clinical centers around the nation by the Asthma Clinical Research Network, which is supported by NIH's National Heart, Lung and Blood Institute (NHLBI).

The study was published in the September 19, 2010, issue of the New England Journal of Medicine. The scientists found that adding tiotropium bromide to low doses of inhaled corticosteroids is as effective at controlling asthma as adding salmeterol. Both are more effective than doubling inhaled corticosteroids alone.

Tiotropium bromide improved patients' day-to-day lung function. It also reduced the number of "asthma control days," when they had to use their albuterol inhalers. Extrapolating from the treatment period, the researchers calculated that the patients had an average of 77 asthma control days per year when the trial began. Doubling corticosteroids gave them an average of another 19 symptom-free days. Adding tiotropium to low-dose corticosteroids gave them another 48.

"Tiotropium relaxes smooth muscle in the airways through a different mechanism than beta agonists, and thus may help people who do not respond well to currently recommended treatments," Peters says. "Further analysis of the study data will help us better understand which patients respond best to tiotropium. Then we will need to conduct longer-term studies to establish its safety for asthma patients and to determine its effect on the frequency and severity of asthma exacerbations."